WCVB | Family of Colleen Ritzer(DANVERS, Mass.) -- The grandmother of Philip Chism, the Massachusetts high school student who allegedly killed his math teacher, said Thursday she feels "sadness and regret" that her grandson could have perpetrated such a grisly crime.

Angelia Chism spoke to ABC News from her home in Tampa, Fla., and said she could not remember the last time she saw her 14-year-old grandson, who is being held without bail on a murder charge.

"We very much want to express our sadness and regret for this," Chism said.

She described her family as religious and said her son, Philip's father, is separated from the teen's mother and is temporarily staying at her home in Florida.

Chism, who uses a walker, said she is recovering from cancer and would be unable to travel to Massachusetts due to her health.

Police are still trying to determine a motive for the murder of Colleen Ritzer, 24.

Philip Chism, who recently moved to Danvers, Mass., with his family, is accused of killing Ritzer with a box cutter on Tuesday and then dumping her body in the woods behind school.

After he allegedly killed Ritzer, police said the teen went to the Hollywood Hits Cinema, where he reportedly watched Woody Allen's Blue Jasmine.